The present invention is generally directed to prototyping and fabricating complex circuits for radio frequency (RF) and microwave frequency ranges. More particularly described, the present invention uses the combination of an optimized monolithic microwave integrated circuit (MMIC) and a single layer or multilayer substrate, such as a conventional alumina substrate, a low temperature co-fired ceramic (LTCC) substrate, a printed circuit board (PCB), a high temperature co-fired ceramic (HTCC), a hybrid ceramic-organic substrate, or a glass substrate, to reduce the conventional time period for fabrication and testing of prototype microwave integrated circuits.
Electronic circuits typically comprise active components and passive components. Typical active components comprise transistors, such as field effect transistors (FETs), bipolar junction transistors (BJTs), and diodes. Passive components typically comprise inductors, capacitors, resistors, and, for high frequencies, transmission lines. A circuit designer can design a functional circuit block by combining active and passive components in a specified configuration. In turn, the circuit designer can combine various functional circuit blocks to realize a more complex circuit design.
An integrated circuit comprises circuits placed upon a single semiconductor substrate. A circuit designer can design a discrete integrated circuit by using numerous components, each having a single dedicated function, such as a transistor, wire-wound inductor, or carbon film resistor. In contrast, a circuit designer can design a hybrid integrated circuit by using only a few components, each typically comprising a complex function. A circuit designer can use both active and passive components for fabrication on a semiconductor substrate. However, selected substrate materials, such as ceramic, are useful only for a placement of passive components (not transistors).
The ongoing computer evolution has pushed the design of digital circuits to an increasingly higher level of circuit integration. Likewise, the growing trend of wireless mobile communications has encouraged designers to create RF and microwave frequency circuits that can be housed within increasingly smaller circuit packages. Highly integrated circuit designs achieve the benefits of smaller circuit size, improved circuit matching, precise control of component layout, and the availability of multiple active components within a small design package. Highly integrated circuit designs also achieve increased circuit repeatability and reliability over corresponding discrete circuit implementations.
Designers of highly integrated digital circuits and RF and microwave circuits face different circuit design and layout criteria. A designer can achieve a highly integrated circuit for a digital application based largely upon the use of active components to achieve a monolithic implementation. In contrast, a designer of highly integrated circuits for RF and microwave frequency applications, typically 100 MHz-10 GHz, faces the design challenge of using matching circuits comprising passive components that consume a large portion of the available semiconductor real estate. For example, at lower frequencies, the passive components can consume more semiconductor xe2x80x9creal estatexe2x80x9d than active components. Consequently, RF and microwave circuit designers faced additional circuit layout challenges as a result of the amount of semiconductor real estate consumed by passive components for matching the impedances of active components.
In addition to circuit layout challenges, an RF and microwave circuit designer also faces extended fabrication times to implement and test a design prototype. For example, current microwave circuit semiconductor technology typically requires 6-8 weeks of foundry processing to achieve a design fabrication. If multiple design passes are required to satisfy performance requirements, an MMIC design may require up to 8 to 16 months of integrated circuit development and foundry time. An alternative design approach requires the use of multiple separate integrated circuits to achieve a single function, where the separate circuits are fabricated in parallel to expedite processing time. Neither approach provides a suitable adaptable design that achieves the short processing times dictated by the rapidly changing demands of the wireless mobile communication marketplace.
In view of the foregoing, there is a need in the RF and microwave frequency design art for a technique to develop MMICs in short fabrication processing time periods. In addition, there is a need in the relevant design art for a technique to achieve adaptable designs for satisfying a variety of application requirements in an efficient and timely manner. The present invention satisfies these and other needs of the prior art based upon the innovative combination of an MMIC array and a multilayer substrate, such as a conventional alumina substrate, an LTCC substrate, a PCB equivalent, an HTCC substrate, a hybrid ceramic-organic substrate, or a glass substrate. The present invention can use an MMIC array to achieve different functional circuit blocks based upon interconnection and design changes to the multilayer substrate, which can be fabricated on a relatively quick turn-around period.
The present invention is generally drawn to a system and method for creating RF integrated microwave circuits that can support multiple applications where many RF functions can be derived from a generic integrated circuit after the integrated circuit is manufactured. More specifically, the present invention can provide active and passive device building blocks of respective monolithic microwave integrated circuit (MMIC) arrays and substrates that can be coupled together in various ways after manufacture of the integrated circuits to achieve multiple applications. One objective of the present invention is to generally reduce the amount of time needed to manufacture RF integrated microwave circuits. This can be accomplished by manufacturing chips with multiple active device blocks that can support various and multiple applications and that can be coupled together in various ways, adjusted, or tuned after manufacture.
Active device blocks of the present invention may include, but are not limited to, transistors, such as field effect transistors (FETs), bipolar junction transistors (BJTs), and diodes. Passive device blocks may include, but are not limited to, inductors, capacitors, resistors, and, for high frequencies, transmission lines.
The present invention can be characterized as a xe2x80x9ctool setxe2x80x9d where the tools can comprise a plurality of active device blocks disposed in an integrated circuit that can be selected by a user after the integrated circuit is manufactured. That is, integrated circuits of the present invention can comprise a first set of active device blocks that can be selected and coupled together to support a desired RF function. Meanwhile, a second set of the active device blocks can remain uncoupled from the first set since the second set of active device blocks may not be needed for a current desired RF function, but the second set of active device blocks can be used for a future RF function.
However, the present invention is not limited to an exemplary embodiment that comprises a first set of active device blocks that are used and a second set of active device blocks that remain unused. It is possible in another exemplary embodiment that all of the active device blocks are coupled together to achieve a desired RF function while unused active device blocks do not exist.
Unlike conventional monolithic microwave integrated circuits which usually couple all active device blocks together, the present invention permits a user to selectively couple active device blocks together while leaving some of the active device blocks uncoupled after the monolithic microwave circuit has been manufactured. This means, that the present invention can support various RF applications even after fabrication of the integrated circuit.
The present invention can eliminate traditional steps in the RF integrated microwave circuit design process. For example, the present invention can eliminate that steps where a user selects desired active and passive device blocks and waits for a foundry to form the integrated circuit that comprises the active and passive device blocks.
In one exemplary embodiment of the present invention, all active device blocks can be placed on a single integrated circuit chip while all passive device blocks can be placed on one or more substrates. The passive blocks can be coupled to corresponding active device blocks on the integrated circuit chip with bond wires and bond pads that may be present on both the substrates and integrated circuit chip.
In another exemplary embodiment, all active device blocks and one or more critical passive device blocks can be placed on a single integrated circuit chip while remaining passive device blocks that are not considered to be critical can be positioned on one or more substrates. A critical passive device block can comprise passive device blocks that require relatively short bond wire lengths to achieve a desired performance level. In other words, a critical passive device block may comprise a passive device block that cannot tolerate performance degradation that can occur because of a bond wire connections that would be needed if the passive device block was placed on a substrate and not on an integrated circuit chip.
In another exemplary embodiment, multiple applications for a contemplated RF integrated microwave circuit can be selected. The multiple applications can comprise primary and secondary applications. Next, a number of primary applications are selected that reduces an amount of the secondary applications. In other words, in this exemplary embodiment, a smaller set of applications can be selected within the larger set of multiple applications that is usually contemplated in other exemplary embodiments. In this exemplary embodiment, the xe2x80x9ctool setxe2x80x9d as described above can be smaller than the xe2x80x9ctool setxe2x80x9d described in other exemplary embodiments. Also, in this reduced size xe2x80x9ctool setxe2x80x9d embodiment, more performance details can be considered when selecting the active device blocks. For example, for each active and passive device block, frequency ranges or bands can be assessed for the selected, reduced set of applications for the RF integrated microwave circuit.